Sophisticated computer and interactive graphic systems such as CAD/CAM written for design and manufacturing have enabled remarkable advances in the fabrication of complex mechanical structures. Such systems have recently been used for medicinal purposes, that is, producing models of sections of the human body for use in surgical planning and/or for the manufacturing of custom protheses. See, for example, the article entitled "System Integration for the Manufacturing of Custom Protheses and Anatomic Models" by M. L. Rhodes et al, which appeared in the proceedings of the international symposium of computer assisted radiography presented in Berlin, West Germany in 1987.
It is becoming more common for surgeons to utilize three dimensional models made from CT image data for pre-operative planning. The pre-operative planning results in a higher rate of successful operations. Without the custom image analysis brought about by utilization of three dimensional models, the types of protheses or implants available were made in standard sizes.
There are occasions when standard protheses cannot be used. For example, custom protheses are needed for patients who have congenital degenerative disease or need limb sections due to carcinogenic or traumatic disorders or for patients who are young and active. When the standard off the shelf protheses were used in the past the adjustments were made by sculpting the patient's anatomy in order to have a firm stable functional reconstruction. Removal of skeletal mass for implanting protheses is dangerous and reduces the natural reliability of the patients skeleton.
Presently, most of the three dimensional anatomical models are manufactured using CAD/CAM techniques along with expensive tool machines. Most hospitals are not in a position to purchase CAD/CAM equipment and expensive tool machinery for the relatively few times that three dimensional models are needed for pre-operative studies. Accordingly, those skilled in the art are attempting to reduce the cost and the complexity of the equipment needed to produce three dimensional models.
In non-related fields, attempts are also being made to reduce the costs of producing models. For example, an article which appeared in the magazine "Machine Design" on Mar. 6, 1986 entitled "Sculpting with Light" by E. V. Fudim describes a plastic forming process for use in producing complicated parts or models of complicated parts without the necessity of extensive tool machine operations. The process described is a type of photographic process wherein a "mask" provides light and shadow patterns in the form of the part to be constructed. The pattern is directed onto a light sensitive polymer of the type which when exposed to light hardens while the portion in the shadow remains liquid. Thus, sheets of polymer described by the light and shadow pattern of the mask can be produced. Multiple masks can be stacked to produce multilayer parts.
Another device for producing models with photographic like processing is described by "Newsweek" magazine, in the issue of Nov. 23, 1987 on page 3. Therein, the process of building three dimensional plastic prototypes from computerated designs, is described. Apparently, the light used in a photographic technique is controlled by CAD/CAM computerized program. For example, the article describes a "galvananometer mirror scanner" driven by computer generated vectors, to move an ultra-violet laser generated small intense spot of light across the liquid in a pre-programmed pattern, for hardening or photo-polymerizing the plastic in the regions required almost immediately.
Thus, in the described light sensitive manufacturing methods, either special masks are made for providing the light patterns to the photo plastic polymer or CAD/CAM programs are used. To date no use has been made of masks and photo sensitive processes for producing anatomical models. For example, an article of the Computer Assisted Radiology proceedings (CAR'87) at pages 416-423 describes using CT scanner data to feed a CAD/CAM programmed computer to drive expensive tool machines to provide desired models.
Accordingly, there is still a need in medical diagnostics for improving the method of manufacturing three dimensional anatomical models and for improving the final models. The method of manufacturing the models should be inexpensive and use a minimum of equipment and/or outlay for new equipment at the hospitals.